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Soixante annees d'evolution des concentrations atmospheriques en mercure elementaire gazeux reconstruites grâce aux archives glaciaires du Groenland

Abstract : Mercury, a toxic metal emitted to the environment via both natural and anthropogenic sources, is found generally in the elementary gaseous form (Hg°) in the atmosphere. The natural cycle of this pollutant has been perturbed by humans for some time, however the importance of these alterations remains as yet poorly characterised. The air from polar firn constitutes a historical record of the atmosphere's composition which has, until now, never been used to study the mercury cycle. In 2005 and 2006 at Summit, Central Greenland, we observed reactive mercury chemistry in the first three metres of the snowpack, which translated to daily and seasonal variations in Hg° concentrations in the interstitial air of the snow. However, we determined that these processes do not affect the atmospheric records in deep firn. We measured Hg° concentrations in the interstitial air of the firn at Summit at depths between 15 and 79,5 metres and were able to establish a transfer function. This function was then used to reconstruct past atmospheric Hg° concentrations in mid to high northern latitudes from 1950 to the present. The reconstructed signal illustrates a maximum of ~3 ng.m-3 in ~1970 and reproduces the stability in atmospheric mercury concentrations observed since 1995. Our model also highlights the strong influence of human activities on atmospheric mercury concentrations. The atmosphere, a highly active chemical sink for atmospheric mercury, allows for a rapid transfer of this pollutant to other oceanic and continental reservoirs where it can be deposited in divalent forms which become available for methylation and subsequently, the contamination of ecosystems.
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https://tel.archives-ouvertes.fr/tel-00202444
Contributor : Xavier Faïn <>
Submitted on : Sunday, January 6, 2008 - 10:33:33 PM
Last modification on : Monday, May 18, 2020 - 2:30:47 PM
Document(s) archivé(s) le : Tuesday, April 13, 2010 - 4:22:00 PM

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  • HAL Id : tel-00202444, version 1

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Xavier Faïn. Soixante annees d'evolution des concentrations atmospheriques en mercure elementaire gazeux reconstruites grâce aux archives glaciaires du Groenland. Océan, Atmosphère. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00202444⟩

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